1. Field of the Invention
This invention relates to a heat exchanger, and more particularly to a heat exchanger which is used as a condenser installed in an air conditioner for an automobile and the like.
2. Description of the Related Art
In FIG. 5 and FIG. 6 which show conventional heat exchanger, fins 5 and tube elements 6 are alternately stacked together. First and second tank elements 3, 4 are installed on both sides of the fins 5 and the tube elements 6. The coolant, before flowing into the heat exchanger, is high temperature steam. At first the coolant flows into an entrance 1 and inlet pipe 2 and runs in an inner space 3d of first tank element 3, which is divided by partition wall 9. After that it runs through the tube elements 6 and each inner space 4d, 3e, 4e of the first and second tank element 3, 4, as shown by arrows 6A, 6B, 6C, and flows through outlet pipe 7 and outlet pipe 8.
The coolant flow exchanges heat with cooling air-flow shown as an arrow 15 through the surface of the tube elements 6 and the fins 5. As a result of this heat exchange, the heat of the coolant flow is removed by the cooling air-flow. As the coolant flow is cooled, it is compressed and liquefies, and its volume decreases. Considering the decrease of the volume of the coolant flow, the total cross-sectional area of the tube elements 6 needed to carry the coolant flow becomes smaller as the coolant flow runs from the entrance to the exit as shown in FIG. 5. In general, the tube elements 6 and the tank elements 3 are formed by extrusion molding. They are constructed and soldered to the fins 5.
The heat exchanger shown in FIG. 5 is a an orthogonal flow type, namely the coolant flow intersects at right angles with the cooling air flow. Though the shape of the orthogonal flow type is compact, the heat exchange efficiency is less than that of the opposite flow type (the coolant in the opposite flow type flows opposite to the cooling air flow) in general. Because the heat of the coolant is removed and the temperature of the coolant goes down between the upper reaches and the lower reaches of the exchanges, the difference between the two flows is slowly reduced.